Explain how it is possible to differentiate bacteria able to invade cultured epithelial cells from those only able to attach to the surface, and to determine the number of internalized bacteria...

Explain how it is possible to differentiate bacteria able to invade cultured epithelial cells from those only able to attach to the surface, and to determine the number of internalized bacteria (without using a microscope!).

Critique the following statement: if you compare the genomes of a pathogen and a closely related nonpathogen (e.g., S. enterica serovar Typhimurium and E. coli K-12), the differences will be the virulence genes.